New Formulation of the Type IIB Superstring Action in AdS₅ X S⁵

Previous studies of the type IIB superstring in an AdS_5×S^5 background are based on a description of the superspace geometry as the quotient space PSU(2,2|4)/SO(4,1)×SO(5). This paper develops an alternative approach in which the Grassmann coordinates provide a nonlinear realization of PSU(2,2|4) based on the quotient space PSU(2,2|4)/SU(2,2)×SU(4), and the bosonic coordinates are described as a submanifold of SU(2,2)×SU(4). This formulation keeps all bosonic symmetries manifest, and it provides the complete dependence on the Grassmann coordinates in terms of simple analytic expressions. It is used to construct the superstring world-sheet action in a form in which the PSU(2,2|4) symmetry is manifest and kappa symmetry can be established. This formulation might have some advantages compared to previous ones, but this remains to be demonstrated